A sign that you may be in a healthy relationship is that you're sharing.
You still have a strong sense of self (that is, you are still thriving), but you and your partner are thinking more like each other. You're a team.
What happens in a healthy relationship when you are sharing?
Gratitude.
Neither of you are experiencing your love for each other as a burden, even if you both recognize it as a sacrifice.
You feel that your partner's acts of love are done for your sake, not the sake of the relationship. Your partner feels the same.
You and your partner receive each other's acts of love with gratitude.
As you share in gratitude and appreciation for each other, you both feel secure, not anxious, about the status of the relationship.
Interdependence.
Your and your partner's emotions are linked. You still have a unique experience that is distinct from your partner's, but you are in tune with your partner. You feel joy when your partner feels joy, and you feel sadness when your partner feels sad, even if you aren't consumed by that sadness.
Mutuality.
You have found a balance. Neither you nor your partner feels depleted just so that the other can feel full.
Your relationship is one where there is mutual giving and accepting -- not taking.
In a healthy relationship, you prefer to prefer what your partner prefers.